Frequency dependence of the two-photon absorption coefficient in InSb: tunneling effects

Abstract
The two-photon absorption coefficient β of InSb was carefully determined at 9.6 and 10.6 µm, using simultaneous self-induced refraction and transmission measurements of 45-psec CO2 laser pulses. It was found that the frequency dependence of β was quite different from a previous measurement using nanosecond laser pulses [A. M. Johnston, C. R. Pidgeon, and J. Dempsey, Phys. Rev. B 22, 825 (1980)]. The discrepancy is believed to be due to the uncertainty in the recombination and diffusion rates for the nanosecond experiments. The new results reported here are consistent with the theory of tunneling-assisted ionization in a narrow-band-gap semiconductor.